Retinoic Acid Receptors Inhibit AP1 Activation by Regulating Extracellular Signal-Regulated Kinase and CBP Recruitment to an AP1-Responsive Promoter

Abstract

Retinoids exhibit antineoplastic activities that may be linked to retinoid receptor-mediated transrepression of activating protein 1 (AP1), a heterodimeric transcription factor composed of fos- and jun-related proteins. Here we show that transcriptional activation of an AP1-regulated gene through the mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERK) pathway (MAPK^ERK) is characterized, in intact cells, by a switch from a fra2-junD dimer to a junD-fosB dimer loading on its promoter and by simultaneous recruitment of ERKs, CREB-binding protein (CBP), and RNA polymerase II. All-trans-retinoic acid (atRA) receptor (RAR) was tethered constitutively to the AP1 promoter. AP1 transrepression by retinoic acid was concomitant to glycogen synthase kinase 3 activation, negative regulation of junD hyperphosphorylation, and to decreased RNA polymerase II recruitment. Under these conditions, fra1 loading to the AP1 response element was strongly increased. Importantly, CBP and ERKs were excluded from the promoter in the presence of atRA. AP1 transrepression by retinoids was RAR and ligand dependent, but none of the functions required for RAR-mediated transactivation was necessary for AP1 transrepression. These results indicate that transrepressive effects of retinoids are mediated through a mechanism unrelated to transcriptional activation, involving the RAR-dependent control of transcription factors and cofactor assembly on AP1-regulated promoters.

We thank R. M. Evans (Salk Institute), J. D. Chen (University of Massachussetts), V. Cavailles (INSERM U148, Montpellier, France), D. D. Moore and B. W. O'Malley (Baylor College of Medicine), S. Michel and U. Reichert (CIRD-Galderma), L. P. Freedman and C. Rachez (MSKCC, New York, N.Y.), M. Yaniv (Institut Pasteur, Paris, France), J. M. Blanchard (I.G.M., C.N.R.S. Montpellier), Jim Woodgett (Ontario Cancer Institute), R. G. Davis (H.H.M.I., University of Massachusetts Medical School), and M. Nemer (I.R.C.M, Canada) for providing us with DNAs, retinoids, and antibodies. We thank C. Rachez and P. Sacchetti for careful reading of the manuscript and B. Masselot for technical help.

INSERM U459 is part of IFR 22 (INSERM, C.H. and U. de Lille, C.O.L. and University of Lille 2). This work was supported by grants from INSERM, Association pour la Recherche sur le Cancer and Ligue Nationale contre le Cancer (Comité du Nord-Pas de Calais).